Caption: Eye. Artwork showing the eye in cross-section on a face in profile. The eye is the organ of sight. The cornea (yellow) focuses light through the hole in the iris (blue) called the pupil (black). The light then falls on the lens (pale blue) which focuses it onto the retina (red) at the back of the eye. The eye itself is filled with a liquid called vitreous humour, which helps the eye maintain its shape. Signals from the retina travel along the optic nerve (orange) to the brain.